Clarification and Application of Turbulent Mixing for Hydrogen Air Supersonic Mixing

本研究分为掺混评价和掺混强化两个部分。首先，利用铂丝催化反应对超音速掺混条件进行了时间序列评价，并进行了实验研究。从喷射器向超音速自由气流(马赫数为1.81)中注入气态氢气。利用具有铂丝和参照丝(镍丝)的W型探头评价了超音速混合的时间序列条件。评估是通过同时测量保持导线温度恒定的每个电路所提供的各个电力来完成的。对铂丝的具体供电取决于催化放热速率(给出氢气浓度)和流动对流。同时，对镍丝的作用依赖于流动对流。结果表明，随着混合的发展，这些电功率之间的相关系数增大。此外，还进行了氦、空气和无二次i…的调查。与氢气喷射器的情况相比，有更多的注氢情况。结果表明，利用该方法可以测量空气-氢气超音速混合层的时间序列行为或湍流的相干运动。其次，对于超音速混合增强，实验表明大尺度的流向涡似乎是最有利的，例如，质量通量涨落的FFT谱分析表明，功率谱部分遵循Kolmogorov-5/3幂定律，表明流向涡的破裂是产生高混合功率的小尺度湍流涡的原因。本文利用PIV、纹影显示、热线风速仪和CFD研究了流向涡的破裂过程。实验结果表明，在涡雷诺数ReΓ=Γ/v=1.3×10~(-4)或更大时，流向涡发生破裂为小尺度湍流，流向涡的横向结构参与了其破裂过程。计算分析表明，斜坡处剪切层的振荡会导致流向涡的不稳定，从而导致流向涡的破裂。较少

This research has two parts of the mixing evaluation and mixing enhancement.First, an experimental study was carried out to confirm the validity of time series evaluation of supersonic mixing condition by using catalytic reaction on a platinum wire. Gaseous hydrogen was injected into supersonic free-stream (Mach 1.81) from injector. Time series condition of supersonic mixing was evaluated by using W-type probe which has a platinum wire and reference wire (nickel wire). The evaluation was done by simultaneously measuring each electric power supplied by each electric circuit which kept the temperature of wire constant. Specifically supplied electric power to Pt wire depended on catalytic heat release rate (giving hydrogen concentration) and flow convection. Meanwhile that to Ni wire depended on flow convection. The result showed that correlation coefficient between these electric powers increased when mixing developed. Investigations were also conducted for helium, air and no secondary i … More njectant cases to compare with the hydrogen injectant case. The results indicated that it was possible to measure the time-series behavior of air-hydrogen supersonic mixing layer or coherent motion of turbulence by using this evaluation.Second, for supersonic mixing enhancement, experiments suggested that large scale streamwise vortices seemed to be the most advantageous, for example, FFT spectrum analysis of mass flux fluctuations showed that the power spectrum partly follows Kolmogorov's -5/3 power law, indicating that the breakdown of streamwise vortices occurred to generate small scale turbulent eddies of high mixing power. The present study examined the breakdown process of streamwise vortices by using PIV, schlieren visualization, hot-wire anemometer and CFD. The experimental results showed that the breakdown of streamwise vortices into small scale turbulence occured at the vortex Reynolds number ReΓ=Γ/v=1.3×10^4 or more, and that the lateral structure on streamewise vortices took a part in its breakdown process. From the computational analysis, the oscillation of shear layer from ramp could make the streamwise vortices unstable and cause its breakdown. Less